Paul O’Connell has been ruled out of the opening game of the Guinness Series against South Africa due to a back injury.
O’Connell returned to training at the start of this week and took a full part in the squad sessions on Monday and Tuesday, but suffered a reaction and will not be fit for selection for this weekend’s game.
The player will see a specialist in the coming days and an update will be issued in due course.
The absence of the 2009 British and Irish Lions captain will come as a huge blow to Ireland head coach Declan Kidney, who is already without the services of captain Brian O'Driscoll and Ulster hooker Rory Best.
However, with Kidney much maligned in the past for failing to try out new options when possible, these enforced absences could lead to a new-look and untried Ireland side, which many Ireland fans have been calling for since Rugby World Cup 2011.
Kidney and his back roomteam will name the team to face South Africa at lunchtime on Thursday.
Ireland squad: Michael Bent (Leinster), Tommy Bowe (Ulster), Darren Cave (Ulster), Tom Court (Ulster), Sean Cronin (Leinster), Gordon D'Arcy (Leinster), Keith Earls (Munster), Declan Fitzpatrick (Ulster), Craig Gilroy (Ulster), Cian Healy (Leinster), Jamie Heaslip (Leinster), Iain Henderson (Ulster), Chris Henry (Ulster), Michael Hurley (Munster), Paddy Jackson (Ulster), David Kilcoyne (Munster), Luke Marshall (Ulster), Paul Marshall (Ulster), John Muldoon (Connacht), Conor Murray (Munster), Mike McCarthy (Connacht), Fergus McFadden (Leinster), Kevin McLaughlin (Leinster), Donncha O'Callaghan (Munster), Paul O'Connell (Munster), Tiernan O'Halloran (Connacht), Ronan O'Gara (Munster), Peter O'Mahony (Munster), Eoin Reddan (Leinster), Mike Ross (Leinster), Donnacha Ryan (Munster), Jonathan Sexton (Leinster), Richardt Strauss (Leinster), Andrew Trimble (Ulster), Dan Tuohy (Ulster), Simon Zebo (Munster).